1. Field of the Invention
The present invention relates to a switch device, and more particularly, to a switch device having a lead-out pattern extending from a second fixed contact provided inside a first fixed contact is covered with an insulating film.
2. Description of the Related Art
A switch device disclosed in Japanese Unexamined Utility Model Registration Application Publication No. 61-68432 will be described with reference to FIGS. 3 and 4. In a switch device 21 shown in FIGS. 3 and 4, a peripheral contact 23 having a broken annular shape is formed on an insulating substrate 22, for example, by printing with silver ink. The peripheral contact 23 includes a cutout portion having a predetermined width, and cutout ends 23a. The insulating substrate 22 is exposed between the cutout ends 23a. 
A portion of the insulating substrate 22 exposed between the cutout ends 23a includes a pair of protuberances 22a that are arranged at a predetermined distance from each other and are formed by extrusion. The height of the protuberances 22a is more than the thickness of the peripheral contact 23.
A center contact 24 is provided inside the peripheral contact 23, and is made of the same material as that of the peripheral contact 23. A lead-out pattern 24a extends from the center contact 24 to the outside of the peripheral contact 23. The lead-out pattern 24a is routed between the protuberances 22a, and is led to the outside.
The lead-out pattern 24a is thinner than the protuberances 22a. A dome-shaped elastic reversing leaf spring (not shown) is positioned on the peripheral contact 23 and on the protuberances 22a. 
A predetermined space is provided between an outer peripheral portion of the reversing leaf spring and the lead-out pattern 24a so that the reversing leaf spring is electrically insulated from the lead-out pattern 24a. 
Operation of the switch device 21 will be described. When the top of the reversing leaf spring, which is disposed on the peripheral contact 23 and the protuberances 22a and is dome-shaped in an initial state, is pressed, the reversing leaf spring is reversed, and a ceiling face of the reversing leaf spring touches the center contact 24. Consequently, the peripheral contact 23 is electrically connected to the center contact 24 via the reversing leaf spring, and a switch circuit is turned on.
When the press of the reversing leaf spring is removed, the reversing leaf spring automatically returns to the initial dome shape by its own elasticity, and the switch circuit is turned off.
Although the outer peripheral portion of the reversing leaf spring and the lead-out pattern 24a are insulated by the protuberances 22a, if dust, such as metal powder, enters the space between the reversing leaf spring and the lead-out pattern 24a, it may electrically connect the reversing leaf spring and the lead-out pattern 24 in the initial state before the reversing leaf spring is pressed. This causes improper operation.
For example, when the insulating substrate 22 is a flexible printed board, the protuberances 22a projecting from the insulating substrate 22 are worn and reduced in height by repetitive pressing of the reversing leaf spring. This may also cause improper operation.